This MPhil focused on optimisation of graphene synthesis and device fabrication via Chemical Vapour Deposition. The primary aim of this work was to determine an optimal process for the fabrication of graphene tunnelling devices. Using analytical techniques to determine the quality of graphene samples after each step in the fabrication methodology under development, insights from these results could be used to develop a procedure which affords graphene devices with improved sheet resistivity, defect density, surface roughness, monolayer coverage and continuity. The optimised method which is proposed in this MPhil is aimed specifically for use in the synthesis of graphene electrodes for tunnelling heterostructure fabrication.High resolution Raman mapping of graphene grown Copper seed substrates showed drastic variation in graphene quality across areas corresponding to different Copper miller surface terminations. Further Raman, Atomic Force Microscopy (AFM) and electrical measurements were performed to investigate graphene quality degradation upon wet-transfer of graphene onto Silicon substrates, which showed that the formation of graphene wrinkles during wet transfer is primarily responsible for the degradation of graphene quality during this step. AFM studies were also performed to determine an optimal annealing process to remove Polymer residues from graphene post-transfer. The sheet resistivity of graphene devices fabricated via the proposed methodology is up to ~3 fold lower than that of commercially available graphene, furthermore graphene wrinkle formation may be avoided improving sample continuity and decreasing surface roughness.
|Date of Award||27 Jun 2017|
|Supervisor||Alain Nogaret (Supervisor) & Andrew Thompson (Supervisor)|
- chemical vapour deposition
- Raman spectroscopy
- Negative Differential Resistance (NDR)